The Piànico tephra: an early Middle Pleistocene record of intraplate volcanism in the Mediterranean

ABSTRACT Distal tephra are a valuable record of the volcano-tectonic evolution of an area under study. Here, we document the case of the Early Middle Pleistocene rhyolitic tephra of Piànico, discovered in the Southern Italian Alps. The geochemical characteristics of Piànico are unique among the distal tephra outcropping in Italy and indicate an intraplate volcanism at the source. The alkali composition and trace elements show a striking resemblance with the rhyolitic complex of the Euganean Hills, located 170 km from Piànico. However, these rhyolites are much older (Oligocene). Alternatively, the source of this intraplate volcanic episode could be located in the southern Tyrrhenian Sea.     

CLAIRE: First light for a gamma-ray lens

The objective of the R&D project CLAIRE was to prove the principle of a gamma-ray lens for nuclear astrophysics. CLAIRE's Laue diffraction lens has a diameter of 45 cm and a focal length of 277 cm; 556 germanium-silicon crystals are tuned to focus 170 keV photons onto a 1.5 cm diameter focal spot. Laboratory measurements of the individual crystals and the entire lens have been used to validate a numerical model that we use to estimate the lens performance for a source at infinity. During a stratospheric balloon flight on 2001 June 14, CLAIRE was directed at the Crab nebula by a pointing system able to stabilize the lens to within a few arcseconds of the target. In 72 min of valid pointing time, 33 photons from the Crab were detected in the 3 keV bandpass of the lens: CLAIRE's first light! The performance of CLAIRE's gamma-ray lens, namely the peak reflectivity for a polychromatic source (9±1%), has been confirmed by ground data obtained on a 205 meter long test range. CLAIRE's measured performance validates the principle of a Laue lens for nuclear astrophysics, opening the way for a space-borne gamma-ray lens telescope that will achieve one to two orders of magnitude improvement in sensitivity over present technologies.     

New periodic solutions of the three dimensional restricted problem

A global review of the symmetric solutions of the restricted problem made in the Introduction opens a window on new symmetric periodic orbits of the two body problem in rotating axes which could be ‘trivially’ continuable to symmetric periodic orbits of the three dimensional restricted problem for small values of μ (see Figure 3). The proof of this possibility of continuation is given in Sections 1, 2, 3 using regularizing variables.     

Multi-Beam Echo Sounders–INS Automatic Latency Calibration

Abstract

This paper presents an automatic, rigorous, and robust method to determine a Multi-Beam Echo Sounder (MBES) and Inertial Measurement Unit/Inertial Navigation System (IMU/INS) latency calibration. The latency may be due to the IMU/INS itself, but also to the time-tagging configuration, which is generally left to the survey systems user. One survey strip over a flat seafloor is the required configuration of line for using this approach, called Multibeam IMU/INS Latency Automatic Calibration (MILAC), standing for MBES to IMU/INS Latency Automatic Calibration. The algorithm considers only data with maximum latency effects and integrates an automatic data selection for this purpose. The latency estimation procedure is based on an iterative Least Square adjustment method followed by a statistical analysis. Our process can deal with beam acoustic refraction caused by the speed of sound in sea water. The accuracy of MILAC is about 2?ms (millisecond) and its average precision of 0.15?ms. MILAC is able to determine the latency with an average resolution of 5?ms. However, the morphology of the survey line is restricted to smooth and regular seafloor and the survey platform should have a relatively high attitude rate.     

La fabrique magnétique du flysch dauphinois (Alpes francaises) : origine et application quantitative

Résumé

Les propriétés magnétiques des schistes, grès et calcaires du flysch eocène de la zone dauphinoise ont été étudiées en relation avec la minéralogie et la structure de ces roches. La susceptibilité magnétique en champ faible est principalement due au paramagnétisme des phyllosilicates (illite et chlorite).

L’anisotropie de susceptibilité correspond à un ellipsoïde aplati qui présente les caractéristiques suivantes : un axe minimal perpendiculaire à la schistosité et un axe maximal parallèle soit à une linéation d’intersection soit à la direction d’étirement maximal.

On présente un modèle mathématique simple permettant d’utiliser le taux d’anisotropie magnétique pour quantifier l’orientation préférentielle des phyllosilicates. Ce modèle testé sur les niveaux les plus phylliteux du flysch donne des résultats en bon accord avec ceux de la goniometrie de texture. Les possibilités et les avantages de cette méthode structure-logique quantitative sont discutés.     

La déformation post-Miocène en Provence occidentale

Résumé

Le but de la présente étude est de caractériser la déformation récente subie par la Provence occidentale, située entre la nappe de Digne à l’est et la faille de Nîmes à l’ouest. Dans un premier temps, la déformation subie par un marqueur sédimentaire qui est à la fois le plus récent possible et le plus uniformément représenté dans la zone étudiée est considérée. Ce marqueur sédimentaire est le Miocène. La caractérisation de la déformation passe par l’étude de la localisation de celle-ci et donc par l’identification des structures actives responsables de la déformation du Miocène. Ces caractéristiques permettent d’estimer la quantité de raccourcissement total accumulé lors des derniers 20 millions d’années. Dans un deuxième temps, on distingue la part de la déformation postMiocène de cette déformation totale. Les marqueurs utilisés sont des surfaces et des objets géomorphologiques repères. Dans ce travail, nous montrons que la déformation en Provence a été de faible importance entre le Miocène et factuel et qu’elle est surtout produite au cours du Miocène. En conséquence, la déformation récente à actuelle est très difficile à localiser et à caractériser. 11 n’y a pas eu de déplacements post Miocène importants de part et d’autre de la faille de la Durance, pas plus d’ailleurs que le long de toutes les discontinuités majeures du domaine étudié. © 2000 Éditions scientifiques et médicales Elsevier SAS     

First experimental investigation of dual-reciprocating drilling in planetary regoliths: Proposition of penetration mechanics

The search for life in the solar system requires sub-surface exploration capabilities of extra-terrestrial bodies like the Moon and Mars. To do so different techniques are being developed: from the classical rotary drilling techniques widely used on Earth to more original techniques like ultrasonic drilling. Dual-reciprocating drilling (DRD) is a bio-mimetic drilling principle inspired by the manner wood-wasps drill into wood to lay its eggs. It was proposed as an efficient extra-terrestrial drilling technique requiring low over-head force. To deepen the understanding of this novel drilling technique, DRD has been tested for the first time in planetary regolith simulants. These experiments are reported here. To do so a new test bench was built and is presented. The soil forces on the drill bit are analysed and the final depth reached by the DRD system is compared to the final depth reached by static penetration. The experiments have shown very high levels of slippage (defined here specifically for DRD). The observations of the surface deformations and the importance of slippage lead to the proposal of DRD penetration mechanics in regoliths. Finally a re-evaluation of previous DRD experiments conducted on low compressive strength rocks also show the high levels of slippage during DRD.     

Processes controlling very low sedimentation rates on the continental slope of the Gonone-Orosei canyon system,NE Sardinia—terrestrial and oceanic significance

The narrow shelf and upper slope immediately above the Gonone canyon head off NE Sardinia represent areas of very low sedimentation rates. Along the sides of the canyon head (1,600 m water depth), the sediment deposits are homogeneous but show alternating light-grey intervals rich in carbonate and dark-grey ones rich in organic matter, possibly related to distal turbidite processes. Deposits older than 50,000 years are already encountered at core depths of 2.50 m, the sedimentation rates varying from 6–21 cm/10³ years in the lower parts of two cores and from 1.5–3 cm/10³ years in the upper parts. At about 35,000 years BP, both cores show a simultaneous drop in sedimentation rate by a factor of 3, probably in response to local mechanisms of channel avulsion. Lithological, mineralogical and geochemical properties reveal the environmental factors which are responsible for the extremely slow sediment accumulation. The southernmost sector of the coast, and partly also of the shelf, consists of Jurassic limestones which supply only small amounts of fine-grained material transported in suspension. During the last sea-level highstand, the accumulation of the Cedrino River pro-delta remained restricted to the coast, the low siliciclastic sediment yields resulting in poor shelf sediment trapping. The present morphology of the canyon head prevented the occurrence of gravity processes in the deeper part of the canyon system, including the coring sites. Accordingly, deposition was mainly fed by hemipelagic material of planktonic origin, together with only moderate terrigenous inputs. On a wider late Pleistocene timescale, seismic data indicate the occurrence of a coarse-grained, layered turbidite facies, implying a very different architecture of the canyon drainage system probably prior to 60,000 years BP.